How to assign specific value for character

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wesleynotwise
wesleynotwise 2017-5-21
评论： Walter Roberson 2017-5-22
I have a cell array of character vectors, let say
A = {'r' 'b' 'g'; 'g' 'r' 'b'; 'b' 'r' 'g'}
how do I change this character to a specific value, eg: r = 0.5, b = 2, g = -3?

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回答（2 个）

Jos (10584)
Jos (10584) 2017-5-21
Here is an easy way:
A = {'r' 'b' 'g'; 'g' 'r' 'b'; 'b' 'r' 'g'}
RGBval = [0.5 2 -3]
[~,loc] = ismember(A,{'r','g','b'})
B = RGBval(loc)
  1 个评论
wesleynotwise
wesleynotwise 2017-5-21
编辑：wesleynotwise 2017-5-21
Thanks. I am thinking to use the following command, but of course it is incorrect because the output is categorical array. Any idea how to correct it?
B = categorical(A,{'r' 'g' 'b'},{'0.5' '2' '-3'})

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Walter Roberson
Walter Roberson 2017-5-21
RGBval('rgb') = [0.5 2 -3];
A = {'r' 'b' 'g'; 'g' 'r' 'b'; 'b' 'r' 'g'};
B = cellfun(@(C) RGBval(C), A);
  2 个评论
wesleynotwise
wesleynotwise 2017-5-22
Sorry. Can you explain what is
RGBval('rgb') = [0.5 2 -3]
It generates a 1x114 double output?
Walter Roberson
Walter Roberson 2017-5-22
RGBval('rgb') is the same as RGBval(['r', 'g', 'b']) which is the same as RGBval([double('r'), double('g'), double('b')] which is the same as RGBval([114, 103, 98]). Characters, except for char(0), can be used as indices for arrays, and a vector of characters is transformed using double() to become a vector of indices.
There is no requirement that you use the minimum-memory data structure for operations if you have enough available memory.

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